ros.usb_cam驱动的安装

1  下载usb_cam:
     http://wiki.ros.org/usb_cam
2  将usb_cam 拷贝到 catkin_ws
3  在catkin_ws中编译:
    $mkdir build
    $cd build
    $cmake ..
    $make
4  将编译好的整个目录拷贝到 ros的share文件夹中运行。
5 运行
   编写usb_cam.launch文件：
  
<launch>
  <node name="usb_cam" pkg="usb_cam" type="usb_cam_node" output="screen" >
    <param name="video_device" value="/dev/video0" />
    <param name="image_width" value="640" />
    <param name="image_height" value="480" />

      <param name="framerate" value="30" />
    <param name="pixel_format" value="mjpeg" />
    <param name="camera_frame_id" value="usb_cam" />
    <param name="io_method" value="mmap"/>
  </node>
  <node name="image_view" pkg="image_view" type="image_view" respawn="false" output="screen">
    <remap from="image" to="/usb_cam/image_raw"/>
    <param name="autosize" value="true" />
  </node>
</launch>
6 roslaunch usb_cam.launch
7 benchmark
  当usb_cam_node已经运行的时候，打开一个新终端然后执行:
  $rostopic hz --window=1000 /usb_cam/image_raw
8 launch文件中的 "pixel_format"参数要根据摄像头种类设定，我就遇到了mjpeg类型和yuyv类型，若出现"Webcam: expected picture but didn't get it..."请考虑修改类型pixel_format参数